1. Field of the Invention
The present invention relates to an endoscope apparatus.
2. Description of the Related Art
At present, a so-called fiber light source in which small light sources are combined with optical fibers is developed. The fiber light source is suitably used as an illumination optical system of an observation apparatus such as an endoscope apparatus to observe an observation target from the distal end of a thin structure.
For example, Jpn. Pat. Appln. KOKAI Publication No. 10-286235 has suggested an endoscope apparatus equipped with a fiber light source in which laser light sources of three R, G, and B colors, optical fibers, and a diffusion plate are combined. The endoscope apparatus according to Jpn. Pat. Appln. KOKAI Publication No. 10-286235 is configured to guide, to the distal end of an endoscope through a light guide, laser lights from an He—Cd laser that is a three-primary-colors (white-light) laser to simultaneously oscillate a blue laser light of 441.6 nm, a green laser light of 537.8 nm, and a red laser light of 636.0 nm that are three primary colors, and from an He—Ne laser to emit a light having a red wavelength of 632.8 nm, and apply the laser lights to a living body that is an observation target through the diffusion plate and an illumination distribution adjustment filter.
In general, when a laser light is diffused and used as an illumination light, the problem is that there is a lack of information regarding lights that are not included in the wavelength of the laser light. That is, it is known that color reproducibility deteriorates when there is a difference of reflectivity of the living body that is an illumination target between the red laser light of 636.0 nm oscillated by the He—Cd laser and lights having neighboring wavelengths, and lights having other wavelengths in a red region. For example, when a light located in the vicinity of 636 nm is hardly reflected but the other lights in the red region are well reflected, the problem is that the illumination target appears dark under laser light illumination even though the illumination target actually appears red.
To address such problems, Jpn. Pat. Appln. KOKAI Publication No. 10-286235 has suggested that color reproducibility can be improved by the addition of the red light of 632.8 nm and that laser lights of multiple red wavelengths be combined.